The lift equation shows that if density increases while velocity remains constant, lift will

• A. Decrease
• B. Increase in proportion to density
• C. Increase with the square of density
• D. Remain unchanged

Answer: (B)

Lift is directly proportional to air density when speed is held constant. In the lift equation L = 1/2 * rho * V^2 * S * Cl, if velocity, wing area, and lift coefficient are fixed, the lift varies linearly with rho. So increasing density increases lift in direct proportion to that density. The other ideas don’t fit: lift does not depend on density squared when velocity is constant, and it doesn’t stay the same if density changes. A helpful way to picture this is that more air molecules in a given volume provide more force on the wing for the same speed, producing more lift.